1. Field of the Invention
The invention relates to a gliding apparatus suited for the practice of ski touring.
2. Background Information
During the practice of ski touring, the binding securing the boot to the ski required in the ascent phase is functionally very different than in the descent phase. This translates into requirements, in terms of safety and strength of the binding, as well as the kinematics of the boot, that vary from one phase to the other. Thus, during the descent, the binding must ensure that the boot is properly retained on the ski, preferably with release of the binding in the event of a fall in order not to injure the skier. During the ascent, the boot should be enabled to rotate about a transverse axis, substantially at the front of the sole of the boot. Therefore, the boot is not immobilized in relation to the ski, and there is no need to release the binding during the ascent.
For the practice of ski touring, manufacturers have proposed various binding solutions including a specific boot front retaining device, or toe-piece, and a specific boot rear retaining device, or heel-piece.
A first solution is to adapt a binding designed for the descent. This binding is assembled on a rotatable plate that is released during the ascent phase and blocked during the descent phase. As a result, the same devices for retaining the boot are used for both the ascent and the descent. A disadvantage of this design is that, generally speaking, these retaining devices are relatively heavy to move during the ascent phase. Such bindings are described in the documents EP-A-1 438 993, DE-10 2007 038506, and EP-A-2 399 654.
A second solution is to adapt a binding designed for the ascent. In this case, the toe-piece is made lighter and incorporates a boot fastening mechanism defining an articulation axis about which the boot pivots during the ascent. During the descent, the boot is retained at the front by the same toe-piece and at the rear by a complementary heel-piece. The lateral release is generally carried out by the heel-piece. The design of the toe-piece must meet the retention requirements of the descent phase, which makes it complex and weighs down the device. These bindings are shown in the documents EP-A-0 199 098 and EP-A-2 300 111.
A third alternative solution proposes bindings having two separate toe-pieces, one being dedicated to the ascent and the other to the descent.
The document EP-A-0 620 029 describes a pivot bearing serving as the toe-piece for the ascent and a sole-clamp forming the toe-piece for the descent. The sole-clamp is comprised of a clamping yoke foldable between the ascent toe-piece and the rear retaining device. This solution implies that the descent toe-piece is to be housed beneath the boot during the ascent phase. Thus, this configuration requires the boot to be elevated in relation to the ski sole during the ascent. The elevational positioning of the boot is unfavorable for the skier's stability and supports.
The document FR-A-2 567 409 describes another variation incorporating a configurable front retaining device including a lever mechanism for alternatively activating an ascent toe-piece or a descent toe-piece. The descent toe-piece incorporates a lateral release mechanism, which weighs down the front retaining device. To activate one of the two toe-pieces, the mechanism causes the displacement of the toe-pieces, which makes it relatively complex. The activation of a toe-piece acts on the retraction of the other, and vice versa. The kinematics of the ascent toe-piece is complex in that the arms, comprising points cooperating with the sole to form the articulation axis of the boot, move both longitudinally and transversely (bringing the points closer together). The descent toe-piece rotates about an axis transverse to the ski. By design, the toe-piece extends vertically (90° rotation) when in the inactive position. This constraint is detrimental because it hinders the rotation of the boot during the ascent phase, as the boot can hardly turn beyond 45°, because the retracted ascent toe-piece limits this rotation. Therefore, this binding is not optimum for the ascent phase, in which the skier needs to turn the boot in relation to the ski by more than 65°. In the assembled configuration, the front retaining device is esthetically unattractive and bulky. In addition, it can cause injuries or accumulates snow, which can disrupt the operation of the lever mechanism.